R's boss Harry Redknapp hopes he can get the best out of the striker where others have failed in the past although he has been warned it will not be easy.
The striker, known as 'Turboman', has never matched his international performances at domestic level and John Lyons, a journalist for SportLife in Chile, says Redknapp has a battle on his hands.
"There's no doubt that Vargas has the attributes to be a huge success in the Premier League - his blistering pace and finishing ability means he will pose plenty of problems for the very best defenders," Lyons explained.
"However, it will largely depend on whether Redknapp can get the best out of him and if he gets the service he needs to thrive.
"He will always be a danger from balls over the top, and could be a big threat playing off a target man, but he also needs quality through balls, the kind Alexis Sanchez played in Chile's World Cup warm-ups, if Vargas is to shine."
Vargas' career never took off in Italy and he has found himself being pushed from pillar to post on loan at Brazil's Gremio, Spain's Valencia and now QPR.